GRASS ASCII vector format specification

Table of contents

A vector map in GRASS native vector format may contain a mix of
primitives including points, lines, boundaries, centroids, areas,
faces, and kernels. The GRASS ASCII vector format may contain also
a header with various metadata (see example below).

The header is similar as the head file of vector binary format but
contains bounding box also. Key words are:

'A': area (boundary) - better use 'B'; kept only for backward compatibility

The coordinates are listed following the initial line containing the
primitive code, the total number of coordinates in the series, and
(optionally) the number of categories (1 for a single layer, higher
for multiple layers). Below that 1 or several lines follow to
indicate the layer number and the category number (ID).

The order of coordinates is

X Y [Z]

In pre-GRASS 6 versions of the ASCII format, the order of coordinates
was different:

Y X

Latitude/Longitude data may be given in a number of ways.
Decimal degrees must be positive or negative instead of using a hemisphere
letter. Mixed coordinates must use a hemisphere letter. Whole minutes and
seconds must always contain two digits (example: use 167:03:04.567;
and not 167:3:4.567).